1. Technical Field
The present invention pertains to athletic footwear and, more particularly to athletic shoes and traction cleats for providing improved traction and comfort for the wearer of an athletic shoe. In addition, the present invention pertains to methods and apparatus for providing adjustability of the traction and comfort afforded by a cleat for a shoe, and for improving the mechanism and method for locking replaceable traction cleats in place in a receptacle mounted in the outsole of a shoe. Further, the invention relates to improving dynamic traction without sacrificing the structural integrity of a cleat.
Although the preferred embodiments of the present invention are described in connection with golf shoes and cleats for golf shoes, it is to be understood that the principles of the invention apply to any shoe on which cleats or similar traction-providing devices are utilized.
2. Discussion of State of the Art
Historically, golf shoes were provided with traction by means of sharp metal spikes that dig into turf. After many years it was realized that these metal spikes damage the root structure of grass on golf courses, particularly on greens, and as a result, plastic cleat structures were developed so as not to damage grass blades and roots. An early example of such a cleat is found in U.S. Pat. No. 6,354,021 (Deacon et al). A refinement of the plastic traction cleat concept appears in U.S. Pat. No. 6,052,923 (McMullin '923), the disclosure in which is incorporated herein by reference in its entirety. In McMullin '923 there is disclosed a cleat having a hub with a threaded stem projecting from its upper surface to threadedly engage a receptacle mounted in the outsole of a shoe. The underside of the hub has plural relatively short traction protrusions, each having a height sufficient to engage blades of grass in turf to provide traction without puncturing the turf. Subsequent developments increased the length and cross section of these plastic but relatively hard traction elements.
The next major development in the art of plastic traction cleats was dynamic traction elements. Specifically, as part of the dynamic traction concept, the underside of the cleat hub is provided with somewhat longer dynamic traction elements that are secured to and project downwardly and outwardly from the hub and flex to spread outwardly under the load of the weight of a wearer of the shoe to effect traction and a cushiony “feel” for the wearer. The cushiony “feel” results from the gradual spreading outwardly of the flexing traction elements as the sole of the shoe is forced against the turf or ground providing a feeling of resilience to the wearer. Examples of cleats that incorporate dynamic traction elements are found in U.S. Pat. Nos. 6,209,230 (Curley '230), 6,305,104 (McMullin '104) and 7,040,043 (McMullin '043); the disclosures in these patents are incorporated herein by reference in their entireties. These cleats are typically secured to a threaded shoe receptacle or connector mounted in the shoe sole by means of a correspondingly threaded stem extending upwardly from the hub.
Cleats having a combination of both flexible (i.e. dynamic) and relatively inflexible (i.e., static) traction elements are also known in the art. See, for example, U.S. Pat. No. 6,834,446 (McMullin '446), the disclosure in which is incorporated herein by reference in its entirety. In operation, under the increasing weight of the wearer of a golf shoe during a walking step, the longer dynamic elements make initial contact with the turf and spread while deflecting toward the shoe sole. The static traction elements are configured to resist deflection when engaging the ground surface and to provide a suitable bearing for supporting weight applied through the shoe sole. The dynamic and static elements may be arranged in alternation around the hub periphery or in any symmetrical or asymmetrical array, depending on the intended static characteristics. If an asymmetrical array is used, it is known from U.S. Pat. No. 6,823,613 (Kelly et al '613) to design the threaded stem, or other connecting member on the cleat, and the threaded receptacle, or other mating connector in the shoe outsole, in a cooperative manner such that the cleat has only one specific rotational orientation relative to the outsole, whereby the positions of the static and dynamic traction elements are predetermined. The disclosure in the Kelly et al '613 patent is incorporated herein in its entirety.
Some golfers prefer the cushiony feel of dynamic traction elements while others prefer the harder feel of static traction elements. In many cases, differences in terrain and the turf can dictate the need for a harder or softer feel and for the nature of the required traction, (i.e., whether static or dynamic or some intermediate therebetween). We have realized, therefore, that there is a need for a shoe and cleat that permits the wearer to select between harder or more cushiony “feels”, and between different levels of dynamic or static traction.
It is also known in the prior art to provide a locking mechanism associated with the connection of the cleat to the shoe-mounted connector to prevent inadvertent loosening of the connection and removal of the cleat. Examples of such locking mechanisms are found in Kelly et al '613 as well as U.S. Pat. Nos. 5,974,700 (Kelly '700) and 7,107,708 (Kelly et al '708), and in U.S. Patent Application Publication No. 2007/0209239 Kelly et al '239) and the disclosures from these patents and published application are also incorporated herein by reference in their entireties. Among these locking mechanisms is one sold under the trademark FAST TWIST® comprising radially facing locking formations on the cleat and receptacle, respectively, operative to inter-engage when the stem has been screwed or otherwise rotatably engaged into the receptacle socket of the shoe-mounted connector. The locking formations on the outer wall of the internally threaded receptacle comprise an annular array of radially outward tooth-like projections, while the locking formations on the cleat include an angularly extending lead-in ramp, a recess and stop member. The tooth-like projection, during stem rotation, forcefully rides over a lead-in ramp before snapping into a recess, and then abuts the stop member to prevent the cleat from being screwed any further into the receptacle socket. The locking mechanisms allow the cleat to be unscrewed for removal and replacement upon exertion of a predetermined level of torque (i.e., typically by means of a special tool) by resilient yielding of the locking formations. The projections and lead-in ramps are typically formed on angularly-spaced, axially-extending webs surrounding the threaded stem and socket. The projection of one locking assembly may have a greater axial extent than the others, with a corresponding lead-in ramp of smaller axial extent. If this projection engages one of the other ramps, it will hold the threads of the stem and socket out of engagement, thereby preventing insertion of the threads at the wrong initial position.
There are several removable cleats being commercialized that utilize both the FAST TWIST® attachment mechanism and dynamic and/or static traction elements. Typically, these cleats utilize a molded first shot base which includes a body member or hub having, on its upper surface, a threaded stem form and a circular array of locking posts angularly spaced and uniformly arranged about a circular hub. Additional polymer material is molded (i.e., a second shot) on the lower surface of the hub to provide the dynamic or static traction elements or legs that extend downwardly and outwardly from the circular hub. The dynamic traction legs, depending of factors such as their length and flexibility, provide traction by: 1) tangling with grass; 2) deflecting upwardly toward the outsole of the shoe and trapping grass between the upper surface of the traction leg and the sole of the shoe; and/or 3) when the shoe slips sideways, absorbing or opposing the force of the lateral slip and folding inwardly toward the cleat axis, whereby the downward or vertical extension of the elements resiliently increases from the extension in the unflexed position.
Conventionally, the requirement that the dynamic traction elements extend from the periphery of the circular hub serves to restrict the downward or vertical extension that the traction element can achieve when providing traction against lateral slip. The present inventors are aware of an effort to mold dynamic legs or elements separately and then secure them to the hub by other than molding the hub and legs as an integral unit. This method, in theory, could allow the dynamic elements to be attached closer to the center of the cleat hub, thereby moving the element flexure point during lateral slip from the hub periphery to a location closer to the hub central axis. As a result, for the same overall height or vertical dimension of a cleat, the dynamic traction elements can be made longer from their proximal ends (i.e., the points of attachment to the hub) to their distal tips. The longer the lengths the dynamic traction elements, the greater is their ability to flex inward toward the axis and extend to provide increased traction during lateral slip. However, the method of separately molding the dynamic elements (as a unit) and then attaching them to the hub by means of a pin, or the like, is both costly and suffers from the possibility of the element unit becoming detached from the hub. In another aspect of the present invention we present a solution to that problem.
Another limitation in the design of prior dynamic traction cleats is the need to provide a substantially solid circular hub in order to accommodate the above described FAST TWIST® locking mechanism. More specifically, the typically six FAST TWIST® locking posts disposed on the cleat hub are required to be equi-angularly spaced in a continuous array about the threaded stem in order to function in concert with the teeth on the FAST TWIST® shoe-mounted receptacle. If the hub can be configured to require less material it would reduce the cost of manufacture. A feature of the present invention addresses this issue.